The upcoming Hollywood feature movie "Blood Diamond," starring Leonardo DiCaprio, promises to cast a spotlight on the role of so-called conflict diamonds in fueling brutal warfare in parts of Africa. In my own country, Angola, funds obtained through the trade in such diamonds helped finance a 27-year civil war, which ended four years ago. And even though Angola's mining areas are technically at peace, diamonds are once again the force behind a different kind of violence that is no less sinister.

This time private security companies, acting on behalf of large diamond corporations, are brutalizing local populations in the name of fighting illegal artisanal diamond mining, known as garimpo . Hundreds of thousands of locals in the diamond-rich, employment-poor provinces are considered garimpeiros because the land on which they have lived and worked as small-scale traditional miners for centuries has been redefined as concessions, or "reserved" areas owned by the corporations.

In the Lundas, the diamond-rich provinces of northeast Angola, even simple acts such as farming, fishing or bathing in a river can result in cruel punishment by the private security companies. (Much of the artisanal mining consists of hand-sifting gravel in river beds and on the banks.)

One morning last April, Francisco Pinto, 17, went fishing in the Lumonhe River in the Cuango municipality, as he did every day. The guards of K&P Mineira, a security company active in the region, forced him to stop because, they claimed, the fish were also included in the diamond concession area they were protecting. When he argued with them, he was beaten and left unconscious.

I have collected almost 100 cases of human rights abuses on the part of security companies in Cuango, the main site of alluvial mining in the Lundas. These include cases of flogging, humiliation, torture, sexual abuse and even assassinations. Sadistic rituals are common, as are symbolic signs of reprimand, such as cutting off a trouser leg as a warning.

Oftentimes I have documented the blatant complicity of the Angolan government in the actions of the private security industry. In Cuango, for instance, the former commander-general of the National Police is majority owner of K&P Mineira, an obvious conflict of interest.

During Angola's civil war, Jonas Savimbi, leader of the chief rebel group, UNITA, used diamond income to fuel his war machine. The United Nations imposed international sanctions against him in response. The industry's role in the conflict sensitized the world to the concept of blood diamonds, trade in which is now regulated under the auspices of the 2003 Kimberley Process Certification Scheme, a voluntary system that imposes requirements on participants to certify that diamonds are conflict-free.

But as the Angolan case shows, the Kimberly Process is grossly inadequate. It applies only to clear-cut civil conflicts between a government and a rebel movement. In the Lundas region, justice is meted out harshly by the diamond companies that certify the diamonds and the security firms protecting them. Government is in effect left to representatives of corporations. "Angola is a foreign country to us," one man in Cuango put it to me recently. "We Angolans are treated worse than animals."

It is in our hands, as Angolans, to change the course of events. But the diamond-consuming countries, such as the United States, have to do their part as well. The United States should explore ways of imposing sanctions on the import of Angolan diamonds until there is a radical change in the situation. Western buyers of diamonds can choose to buy diamonds from elsewhere, thus expressing their concern and protesting in favor of people's lives.

The world needs to take a moral stand now to ensure that human rights are respected in diamond extraction.

Rafael Marques, an Angolan journalist, is the recipient of the 2006 Civil Courage Prize, awarded annually by the trustees of the Northcote Parkinson Fund. He is the author of a human rights report, "Diamonds of Humiliation and Misery" (http://www.cuango.net).